Automatic self-indicating fuse.



PATE T OFFICE.

FRANK B. COOK, OF CHICAGO, ILLINOIS.

UTOHATIC SELF-INDICATING FUSE.

Speciflcation of Letters Patent.

Patented Dec. 7, 1909.

Application filed March 1, 1909. Serial No. 480,602.

I To all 'whom 'it may concem:

Be `it known that I, FRANK B. CooK, a

citizen of the United States of America, re-

` siding at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Automatic Self-Indicating Fuse, of which the following is a specificaton, reference being had to the accompanying drawi ing? illustrating same.

invention 'relates to devices for auto matically indicating the condition of electrical fuses, that is, whether the fuses are in condition to be blown' or whether they have been blown, my princi al objects bein to provide an improved evice of this c ar- 'acter which is verysimple in Construction and Very efiicient in its operation, and to provide an improved fuse wre for such a device, which permits same to be made so as to blow on a very small amperage.

Other objects will be 'apparent from the following specification.

In the accompanying drawings illustrating 'the preferred form of my invention', Figure l is a longitudinal cross-sectional view of aninclosed fuse rovided with the device'of my invention; ig; 2 is a similar view of a modified form of the invention shown in Fig. 1, with portions shown in elevation; and Fig. 3 is a transverse cross-seconal vew of the mproved fuse wire of the invention. i i

Like characters refer to like parts in the several figures.

The invention com rises spring mechanism normally held under tension by the fuse wire so that when the latter is fused or disrupted the spring mechanism will operate and thus indicate the disruption of the fuse wire. In the referred form of my invention I preferab y attach the spring mechanism to one end of the fuse wire and then by pulling on same place the spring mechanism under tension, or in a set position, in which position the fuse wire is soldered or Secured to the opposite end of the fuse so that when the fuse wre"is blown or severed at any point it will release the spring mechanism and cause the latter to spring out from the end of the fuse and thus indicate that the fuse is disru ted.

. n Fig. 1 of the drawings l represents 4 a tubular casing referably of porcelain or some other suitab e insulatng material, and 2 and 3 reprsent suitable metalhc end caps for the casing 1. The casing 1 has a small I longitudinal bore 4 therethrough through extends. The cap 3 is preferably formed with a small hollow cylndrical portion (i thereon in which a metallic plunger 7 is located, the plunger 7 being conductively connected with the portion G by a coil spring 8 which surrounds the plunger 7 and is soldered to these parts preferably as shown. The fusible conductor 5 is attached to. the outer end of the plunger 7 at 9, preferably by solder, and is then extended through the bore 4 in the casing 1 and through the neck like portion 10 of the cap 2. To set the apparatus for operation the fusible conductor 5 is pulled in the direction of arrow ll until the coil splring 8 is compressed as shown in Fig. l, w ereupon the fusible conductor is soldered to the neck-like portion 10 of cap 2 at 12. Now when the fusible conductor 5 is blown or disrupted in any nanner the plunger 7 is released whereupon the coil spring 8 automatically springs out away from the end cap 3 and thus moves the plunger 7 to the position 13 shown in dotted lines. When the plunger 7 is seen in the position 13 it is known that the fuse wire 5 is blown or that it is disrupted. f

In order to re-fuse the device and set same for operation it is only necessary to supply a new fuse wire 5 thereto, solderng same to the plunger 7 at 9 and then stretching the wire 5 through the fuse casing l in the direction of arrow 11 and solderin it at 12. It will be readily seen that the devce may be reset and operated as many times as desired.

In order to properly utilize this invention it is necessary to employ a fuse wire having considerable tensile strength, so that it may be pulled upon considerably to set the device for operation and also be able to stand the stress of the Operating spring for a long period without being disrupted. In such indicating fuses which are required to operate pere, the ordinary soft lead fuse wire cannot be used, because the tension put upon the wire in setting the in'dicating device will rupture the wire. Neither is it advisable in some such fuses to employ a fuse wire of high resistance. As a fuse wire to overcome these objectons and meet the required conditions I preferably employ in this invention the double-metal fuse wire described in my copending application for Letters Patent on in' ividual protector, Serial No. 437 ,7 22, filed on a very small amperage, say i of an am-,

which the fusible conductor or fuse wire 5 i June 10, 1908. This fuse wire has a steel core 20 to give great strength to the wire and a copper sheath or covering 21 surrounding the core to give high conductivty to the wire. The copper sheath also protects the steel .core from corrosion or deterioration. The advantages of such a wire in such a device can be readily seen.

The double-metal wire used in this invention is preferably made by rolling or drawing it from a steel ingot having a Copper jacket placed therearound.

In the device shown in Fig. 2 there is no indicating plunger employed, this device consisting merely of a coil spring 14 suitably mounted. on a small hollow cylindrical portion 15 having a shoulder at 16 and a somewhat larger cylindrical portion at 17,

'the spring 14 being soldered to the shoulder 16 at 18. In this device the fusible conductor 5 is soldered to the spring member 14 at 19. The spring member 14 is compressed as shown in Fig. 2 when the fusible conductor 5 is pulled in the direction of arrow 11, the same as in the device shown in Fig. 1. When the spring member 14 is suitably compressed, the fuse wire 5 is soldered to the end cap 2 at 12 as hereinbefore stated, which sets the device for operation. When this device operates, that is, when the fusible conductor is blown or becomes disrupted, the coil spring 14 is simply released whereupon it sprin s out away from the end cap 3 and thereby ndicates that the fuse wire is disrupted. This device may be reset for another operation by supplying a new fuse wire 5 thereto, first soldering the fuse wire to -the spring 14 at 19, then pullingthe fuse wire 5 through the fuse casing in the direction of arrow 11 sufliciently to com ress the spring 14, and then soldering the use wire 5 to the 'cap 2 at 12.

In the fuse of this invention the coil spring keeps the fuse wire stretched tightly and therefore 'keeps the wire away from the sides of the bore 4 in the casing 1, if the bore 4 is not too small in diameter. This construction causes the fuses to blow very uniformly because the heat is not conducted away from the fuse wires through the fuse casings, as is the case with ordinary fuses in which the heat is conducted away from the fuse wires very ununiformly.

I do not wish to limit this invention to all of the particular details of Construction herein shown, as many modifications in same may be made without departing from the scope of the appended claim.

lVhat I claim as my invention is:

A fuse of the character described having a casing for the fusible conductor and metallic end caps on the casing, at least one of the end Caps having ahollow outward'ly-projecting hub thereon, a metallic plunger carried within the said hub and movable therein, a coil spring encircling the said plunger and being conductively attached to the latter and to the said hub, and a fusible conductor extendin through the said casing and through the sai plunger and being attachedto the outer end of the latter, the said fusible conductor being normally under tension *whereby the col spring is held under compression to normally hold the said plunger down into the said hub, the fusing of the fusible conductor releasing the said coil sprin and thereby permittn same to extend itse f and thus move the sai plunger outwardly, rela tively to the said hub, for purposes substantially as described.`

As inventor of the foregoing I hereunto subscribe my name the 24th day of February,

FRANK B. COOK. Witnesses: i

FREDERICK R. PARKER, FRANCES K. PARKER. 

